. >> it could be a key to cheaper energy, or an environmental plague. how you view fracking depends on how you weigh the pros and cons. scott drills into a controversy that could affect us all. >> this is not about the kind of gas used by most cars. it's about natural gas, also called "methane." it's a fuel used for everything from cooking food, to heating homes, to even generating electricity. natural gas comes from deep underground. it's trapped amid layers of shale rock. to release the gas, you have to break apart the rock. that process is called "fracking," and that's what the controversy is all about. >> ♪ water goes into the pipe ♪ the pipe into the ground ♪ the pressure creates fissures 7,000 feet down ♪ ♪ the cracks release the gas that powers your town ♪ >> that's from a video produced by propublica. they're a group looking into whether fracking is safe. according to those in favor of fracking, it's not a threat. >> fracking has been used in the united states for decades, and it was developed quite a long time ago to do exactly what